Re: best use of an EMC SAN

We do something similar here. We use Netapp and I carve one aggregate
per data volume. I generally keep the pg_xlog on the same "data" LUN,
but I don't mix other databases on the same aggregate.

In the NetApp world because they use RAID DP (dual parity) you have a
higher wastage of drives, however, you are guaranteed that an
erroneous query won't clobber the IO of another database.

In my experience, NetApp has utilities that set "IO priority" but
it's not granular enough as it's more like using "renice" in unix. It
doesn't really make that big of a difference.

My recommendation, each database gets it's own aggregate unless the
IO footprint is very low.

Let me know if you need more details.

Regards,
Dan Gorman

On Jul 11, 2007, at 6:03 AM, Dave Cramer wrote:

> Assuming we have 24 73G drives is it better to make one big metalun
> and carve it up and let the SAN manage the where everything is, or
> is it better to specify which spindles are where.
>
> Currently we would require 3 separate disk arrays.
>
> one for the main database, second one for WAL logs, third one we
> use for the most active table.
>
> Problem with dedicating the spindles to each array is that we end
> up wasting space. Are the SAN's smart enough to do a better job if
> I create one large metalun and cut it up ?
>
> Dave
>
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